The invention relates in general to sliding surface articles and in particular to a composite material with at least one slide layer, applied by cathode sputtering, of a mixture of particles deposited in statistical distribution of at least one metallic material forming a firmly connected matrix and at least one additional metallic material, which in the solid state is practically insoluble in the matrix material. It relates further to a method for manufacturing such composite materials as well as use of the same in friction bearing shells.
As surface layers slide layers of composite materials are used, for example, for bearing shells of internal combustion engines and must, in addition to others, have the following properties: lower hardness than the material of the shaft, high strength with respect to alternating dynamic stress, high shearing resistance, heat stability of the mechanical properties as well as high corrosion resistance. These requirements are fulfilled, among others, by compositions of lead or tin with metals, which lend the layer mechanical strength by forming a cohesive matrix, they are themselves corrosion resistant and do not process solubility for tin or lead, like aluminum, chromium, or nickel, for example. Such composite materials having lead or tin containing slide layers as well as methods for their manufacture through cathode sputtering are described in German patent Nos. 28 53 724 and 29 14 618 as well as in German OS No. 34 04 880.
When using such slide layers as surface layers, high opposite demands are frequently made of the particular preform or machine part. If applied for friction bearings they should, at least at particular sites, transfer the forces to which the bearing is subjected, with sufficient long life, onto the surrounding structure (load bearing capacity) in order to tolerate the surface pressure of the connecting rods. This requires relatively high heat-stable hardness of the particular slide layers and 70 HV 0.002 has been shown to represent a critical values, which should not be fallen below. Also, from other places of the same machine part, particularly from its slide layers, good embedding response is demanded, i.e. the ability to withstand embedding of dirt or wear and tear particles into the surface. Through such property the danger of damage to the slide surfaces is decreased. In order to meet this demand, the slide layers should not be too hard. Based on experience, hardness of 70 HV 0002 represents also in this connection a critical value, which already requires relatively elaborate measures to protect the particular bearing from entering dirt particles and to keep the lubricant clean through filtration.
In the case of the slide layers described in the state of the art applied by cathode sputtering such contradictory demands made of one and the same machine or preform part cannot be met, since the slide layers in question have identical properties over their entire surface.